The present invention relates to new devices and methods used in providing an electromechanically operated annular flow safety valve in the tubing of a cased subterranean well.
Safety valves are used in subterranean wells to prevent uncontrolled fluid flow, which if not controlled could lead to equipment damage or a catastrophic well blowout. Conventional safety valves generally use a flapper mechanism with a sealing member in the form of a circular disc. Such safety valves are typically constructed with a bias spring mechanism maintaining a closed position, and a hydraulically operated actuator for moving the sealing member to an opened position. Similar safety valves with ball closure mechanisms are also known in the art. It is generally known to control safety valves with a wireline connection to the surface. Some valves have also been designed to close in response to a predetermined pressure. Examples of prior art safety valves are disclosed in U.S. Pat. Nos. 3,990,508; 4,160,484; 4,372,392; and 6,079,497.
Problems exist with downhole safety valves known in the art. Wireline control connections and hydraulic pressure sensors both impose limits on the operating environment of common safety valves. Two of the most important limitations are that of depth and pressure. Physical control connections are more difficult to maintain with increasing depth. Likewise, hydraulic systems are more difficult to operate at the high pressures often found in deep wells. Physical control and sensor mechanisms also have the serious disadvantage that it is required to remove the valve from the well to change pre-selected actuation parameters. Flapper valves are further limited by their one-directional nature. Flapper valves and ball valves are both subject to corrosion from particles that are often found suspended in well fluids. There is a need for improved safety valves with increased flexibility in terms of operating environment and control parameters. There is also a need for safety valves that will undergo minimized erosion damage during use.
The present inventions contemplate improved annular flow safety valve apparatus and methods in which the valve comprises a bi-directional self-contained electromechanically operated valve assembly including a moveable seal, power source, electric motor, and control system. The improved safety valve is capable of operating with or without power or control inputs from the surface. Features are also provided to decrease the erosive effect of solids suspended in the fluid stream.